Boxelder bugs can be a nuisance from fall through spring in and around your home. The picture to the far left is an adult boxelder bug. They find crevices, cracks in walls, doors, foundations and crawl inside. On warm sunny days they are often found on the exterior of west or south side of buildings. As you can see from the picture on the left, these adults are flat-backed, elongate and narrow about 1/2 inch long, 1/3 inch wide and e a dark brownish-black with three lengthwise red stripes on the pronotum or area behind the head. There are three veins in the wings and the abdomen is bright red under the wings which you cannot see in the picture.
Typically, the boxelder bugs feed on a variety of plants. Their favorite food are the seed pods of boxelder trees and then occassionally maple seeds. So if you have a female boxelder tree then you might expect to see boxelder bugs. They also feed on sap of these trees as well as fruit trees. The above picture of leaves is a sample of boxelder leaves courtesy of Cornell University Extension.
The boxelder tree is a maple, Acer negundo which grows best along rivers or streams. It is found in Colorado along riverbanks but is also found in flood plain areas. These trees have very soft wood with no commercial value. Their seeds germinate easily and can become a weedy species. So, if you do place this in your landscape, plan on being overrun with boxelder trees and bugs.
Boxelder bugs are just a nuisance. In late summer the second generation crawl down to the ground and the adults and large nymphs begin to congregate in large numbers. They migrate to a protective, warm place to overwinter. They come out of hibernation in late March and females begin laying rusty red eggs in groups during late April or early May. The eggs hatch in 11 to 19 days and begin their five nymphal instars. The instars become progressively darker red with each stage. The first-generation nymphs feed on boxelder seeds, various low-growing plants and recently dead insects. These first-generation nymphs become fully grown by early summer. Then, a second generation occurs in late summer and the eggs are laid, more exclusively on boxelder seeds. The adults from the second generation begin to congregate, migrate and hibernate.
Other plants that the boxelder bugs feed on are as listed: ash, elm, cherry, apple, peach, grape and strawberries. You may find scarring or dimpling on fruits.
Insecticidal soap is recommended to control the large congregations of boxelder bugs. Once inside the house, they can be killed by direct contact with a household insecticidal aerosol or household spray cleaner. Using a vacuum cleaner can be just as effective. Come late spring or about May, the surviving boxelder bugs move back to their host trees and stop becoming a nuisance for the homeowner.